Traumatic injury of the spinal cord results in permanent functional impairment. Most of the deficits associated with spinal cord injury result from the loss of axons that are damaged in the central nervous system (CNS). Similarly, other diseases of the CNS are associated with axonal loss and retraction, such as stroke, human immunodeficiency virus (HIV) dementia, prion diseases, Parkinson's disease, Alzheimer's disease, multiple sclerosis and glaucoma. Common to all of these diseases is the loss of axonal connections with their targets, and cell death. The ability to stimulate growth of axons from the affected or diseased neuronal population would improve recovery of lost neurological functions, and protection from cell death can limit the extent of damage. For example, following a white matter stroke, axons are damaged and lost, even though the neuronal cell bodies are alive, and stroke in grey matter kills many neurons and non-neuronal (glial) cells. Treatments that are effective in eliciting sprouting from injured axons are equally effective in treating some types of stroke (Boston life sciences, Sep. 6, 2000 Press release). Neuroprotective agents often tested as potential compounds that can limit damage after stroke. Compounds which show both growth-promotion and neuroprotection are especially good candidates for treatment of stroke and neurodegenerative diseases. Similarly, although the following discussion will generally relate to delivery of Rho antagonists, etc. to a traumatically damaged nervous system, this invention may also be applied to damage from unknown causes, such as during stroke, multiple sclerosis, HIV dementia, Parkinson's disease, Alzheimer's disease, prion diseases or other diseases of the CNS were axons are damaged in the CNS environment. Also, Rho is an important target for treatment of cancer and metastasis (Clark et al (2000) Nature 406:532-535), and hypertension (Uehata et al. (1997) Nature 389:990) and RhoA is reported to have a cardioprotective role (Lee et al. FASEB J. 15:1886-1884). Therefore, the new C3-like proteins are expected to be useful for a variety of diseases were inhibition of Rho activity is required.
It has been proposed to use various Rho antagonists as agents to stimulate regeneration of (cut) axons, i.e. nerve lesions; please see, for example, Canadian Patent application nos. 2,304,981 (McKerracher et al) and 2,300,878 (Strittmatter). These patent application documents propose the use of known Rho antagonists such as for example C3, chimeric C3 proteins, etc. (see blow) as well as substances selected from among known trans-4-amino (alkyl)-1-pyridylcarbamoylcyclohexane compounds (also see below) or Rho kinase inhibitors for use in the regeneration of axons. C3 inactivates Rho by ADP-ribosylation and is fairly non-toxic to cells (Dillon and Feig (1995) Methods in Enzymology: Small GTPases and their regulators Part. B.256:174-184).
While the following discussion will generally relate or be directed at repair in the CNS, the techniques described herein may be extended to use in many other diseases including, but not restricted to, cancer, metastasis, hypertension, cardiac disease, stroke, diabetic neuropathy, and neurodegenerative disorders such as stroke, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS). Treatment with Rho antagonists would be used to enhance the rate of axon growth of peripheral nerves and thereby be effective for repair of peripheral nerves after surgery, for example after reattaching severed limbs. Also, treatment with our fusion compounds (proteins) is expected to be effective for the treatment of various peripheral neuropathies because of their axon growth promoting effects.
As mentioned above, traumatic injury of the spinal cord results in permanent functional impairment. Axon regeneration does not occur in the adult mammalian CNS because substrate-bound growth inhibitory proteins block axon growth. Many compounds, such as trophic factors, enhance neuronal differentiation and stimulate axon growth in tissue culture. However, most factors that enhance growth and differentiation are not able to promote axon regenerative growth on inhibitory substrates. To demonstrate that a compound known to stimulate axon growth in tissue culture most accurately reflects the potential for therapeutic use in axon regeneration in the CNS, it is important for the cell culture studies to include the demonstration that a compound can permit axon growth on growth inhibitory substrates. An example of trophic and differentiation factors that stimulate growth on permissive substrates in tissue culture, are neurotrophins such as nerve growth factor (NGF) and brain-derived growth factor. NGF, however, does not promote growth on inhibitory substrates (Lehmann, et al. (1999) 19: 7537-7547) and it has not been effective in promoting axon regeneration in vivo. Brain derived neurotrophic factor (BDNF) is not effective to promote regeneration in vivo either (Mansour-Robaey, et al. J. Neurosci. (1994) 91: 1632-1636). BDNF does not promote neurite growth on growth inhibitory substrates (Lehmann et al supra).
Targeting intracellular signaling mechanisms involving Rho and the Rho kinase for promoting axon regeneration has been proposed (see, for example, the above-mentioned Canadian Patent application nos. 2,304,981 (McKerracher et al)). For demonstration that inactivation of Rho promotes axon regeneration on growth inhibitory substrates, recombinant C3, a protein that inactivates Rho by ADP ribosylation of the effector domain was used. While such a C3 protein can effectively promote regeneration, it has been noted that such a C3 protein does not easily penetrate into cells, and high doses must therefore be applied for it to be effective. The high dose of recombinant C3 needed to promote functional recovery presents a practical constraint or limitation on the use of C3 in vivo to promote regeneration (Lehmann, et al. (1999) J. Neurosci. 19: 7537-7547; Morii, N and Narumiya, S. (1995) Methods in Enzymology, Vol 256 part B, pg. 196-206. In tissue culture studies, it has, for example, been determined that the minimum amount of C3 that can be used to induce growth on inhibitory substrates is 25 ug/ml (Lehmann, et al. (1999) J. Neurosci. 19: 7537-7547; Morii, N and Narumiya, S. (1995) Methods in Enzymology, Vol 256 part B, pg. 196-206. If the cells are not triturated, even this dose is ineffective. It has been estimated, for example, that at least 40 μg of C3 per 20 g mouse needs to be applied to injured mouse spinal cord or rat optic nerve (McKerracher, Canadian patent application No.: 2,325,842). Calculating doses that would be required to treat an adult human on an equivalent dose per weight scale up used for rat and mice experiments, it would be necessary to apply 120 mg/kg of C3 (i.e. alone) to the injured human spinal cord. The large amount of recombinant C3 protein needed creates significant problems for manufacturing, due to the large-scale protein purification and cost. It also limits the dose ranging that can be tested because of the large amount of protein needed for minimal effective doses.
Another related limitation with respect to the use of C3 to promote repair in the injured CNS is that it does not easily penetrate the plasma membrane of living cells. In tissue culture studies when C3 is applied to test biological effects it has been microinjected directly into the cell (Ridley and Hall (1992) Cell 70: 389-399), or applied by trituration of the cells to break the plasma membrane (Lehmann, et al. (1999) J. Neurosci. 19: 7537-7547, Jin and Strittmatter (1997) J. Neurosci. 17: 6256-6263). In the case of axon injury in vivo, the C3 protein is likely able to enter the cell because injured axons readily take up substances from their environment. However, C3-like proteins of the present invention are likely to act also on surrounding undamaged neurons and help them make new connections as well, thus facilitating recovery. After incomplete SCI, there is plasticity of motor systems attributed to cortical and subcortical levels, including spinal cord circuitry (Raineteau, O., and Schwab, M. E. (2001) Nat Rev Neurosci 2: 263-73). This plasticity may be attributed to axonal or dendritic sprouting of collaterals and synaptic strengthening or weakening. Additionally, it has been shown that sparing of a few ventrolateral fibers may translate into significant differences in locomotor performance since these fibers are important in the initiation and control of locomotor pattern through spinal central pattern generators (Brustein, E., and Rossignol, S. (1998) J Neurophysiol 80: 1245-67). It is well documented that reorganization of spared collateral cortical spinal fibers occurs after spinal cord injury and this contributes to functional recovery (Weidner et al, 2001 Proc. Natl. Acad. Sci. 98: 3513-3518). The process of reorganization and sprouting of spared fibers would be enhanced by treatment with C3-like proteins able to enter non-injured neurons. This would enhances spontaneous plasticity of axons and dendritic remodeling known to help functional recovery.
Other methods of delivery of C3 in vitro have been to make a recombinant protein that can be taken up by a receptor-mediated mechanism (Boquet, P. et al. (1995) Meth. Enzymol. 256: 297-306). The disadvantage of this method is that the cells needing treatment must express the necessary receptor. Lastly, addition of a C2II binding protein to the tissue culture medium, along with a C21N-C3 fusion toxin allows uptake of C3 by receptor-mediated endocytosis (Barthe et al. (1998) Infection and Immunity 66:1364). The disadvantage of this system is that much of the C3 in the cell will be restrained within a membrane compartment. More importantly, two different proteins must be added separately for transport to occur (Wahl et al. 2000. J. Cell Biol. 149:263), which make this system difficult to apply to for treatment of disease in vivo.
Retinitis pigmentosa is a retinal degeneration disease which manifests as night blindness, progressive loss of visual field and peripheral vision, eventually leading to total blindness; opthalmoscopic changes can consist in dark mosaic-like retinal pigmentation, attenuation of the retinal vessels, waxy pallor of the optic disc, and in the advanced forms, macular degeneration. In some cases there can be a lack of pigmentation. This disease is hereditary and the degeneration of retinal photoreceptor cell proceeds with increasingly narrower retinochoroidal blood vessel and circulatory disorders.
Diabetic retinopathy, a leading cause of blindness in type 1 and type 2 diabetics, is a complication of diabetes which produces damage to the blood vessels inside the retina. Diabetic retinopathy can have four stages: (1) mild nonproliferative retinopathy, wherein microaneurysms in the retina's blood vessels occur; (2) moderate nonproliferative retinopathy, wherein some blood vessels feeding the retina become blocked; (3) severe nonproliferative retinopathy, wherein many blood vessels to the retina are blocked, depriving several areas of the retina with their blood supply; and (4) proliferative retinopathy, wherein new, abnormal, thin-and fragile-walled blood vessels grow to supply blood to the retina, but which new blood vessels may leak blood to produce severe vision loss and blindness. Hemorrhages can occur more than once, often during sleep. Fluid can also leak into the center of the macula at any stage of diabetic retinopathy and cause macular edema and blurred vision. About 40 to 45 percent of Americans diagnosed with diabetes have some stage of diabetic retinopathy, and about half of the people with proliferative retinopathy also have macular edema.
Stargardt's disease, or fundus flavimaculatus, is a hereditary macular degenerative disorder. Most patients with the condition present in the teenage years with complaints of bilaterally reduced vision. Vision is commonly in the 20/40 range upon first presentation, but frequently falls to the 20/100 level within 4 or 5 years. Vision usually progressively, but gradually, declines beyond 20 years of age, perhaps to the 20/200 level, or worse. Patients will invariably have characteristic flecks in the retina, and these may occupy the macular area in early life. With progression of the disorder, the macula shows atrophy that is not unlike some cases of age related macular degeneration. However, this degree of atrophy is often present in the teens or early 20's. Some patients will develop choroidal neovascular membranes or vessels beneath the retina which may leak fluid or bleed. There is no known treatment that will delay or halt the progression of the disease.
Hypertensive retinopathy involves damage to the retina caused by high blood pressure which produces narrowing of and excess fluid oozing from blood vessels in the retina. The degree of retina damage (retinopathy) is graded on a scale of I to IV, wherein Group I comprises minimal narrowing of the retinal arteries; Group II comprises narrowing of the retinal arteries in conjunction with regions of focal narrowing and arteriovenous nicking; Group III comprises abnormalities seen in groups I and II, as well as retinal hemorrhages, hard exudation, and cotton-wool spots; and Group IV hypertensive retinopathy comprises abnormalities encountered in groups I through III, as well as swelling of the optic nerve head and macula, which can cause decreased vision. Control of high blood pressure (hypertension) is the only treatment for hypertensive retinopathy. Some patients with grade IV hypertensive retinopathy will have permanent damage to the optic nerve or macula. Hypertensive choroidopathy frequently accompanies hypertensive retinopathy when the changes of group IV, and sometimes those of group III, are present. In the acute phase, yellow spots are visible at the level of the retinal pigment epithelium. They are known as Elshnig Nodules. They are hyperfluorescent on fluorescein angiography and appear to occur secondary to fibrinoid necrosis within the choriocapillaris, leading to damage to the overlying retinal pigment epithelium. In severe cases, the intense leakage of plasma from these foci contributes to serous retinal detachment. Over a period of weeks, these spots become pigmented or depigmented. When the spots occur in a linear fashion, they are referred to as Siegrist's streaks.
Occlusive retinopathy or retinal vein occlusion, second only to diabetic retinopathy as a cause of visual loss due to retinal vascular disease, comprises both branch and central retinal vein occlusion in which a portion of the circulation that drains the retina of blood becomes blocked, causing back-up pressure in the capillaries, dilated blood vessels, hemorrhages, swelling (edema), and leakage of fluid and other constituents of blood in the distribution of the vein. An occlusion of the central retinal vein involves the entire retina. Complete vein blockage leads to intense hemorrhages and edema, and involved capillaries can cease to function and close off (ischemia or capillary non-perfusion). Complications of branch retinal vein occlusion include macular edema, macular ischemia (non-perfusion) and neovacularization (growth of new abnormal blood vessels). When the distribution of the vein involves the macula, bleeding and exudation or leakage occurs there to produce macular edema with blurred vision and loss of portions of the field of vision. Scar tissue may form on the surface of the retina to produce a macular pucker or an epiretinal membrane may result in distorted vision (metamorphopsia). With significant closure of capillaries, abnormal vessels may grow (neovascularization) and bleed into the overlying ocular cavity in the posterior part of the eye (vitreous hemorrhage) leading to retinal detachment. Central retinal vein occlusion is closure of the retinal vein located at the optic nerve; the occlusion can be non-ischemic or ischemic. Some central retinal vein occlusions are associated with a significant obstruction of capillaries or non-perfusion, and predisposition to neovascularization that occurs in front of the eye on the iris (rubeosis irides). These eyes may develop a very high pressure (neovascular glaucoma) due to obstruction of the fluid outflow channels, and experience severe vision loss, pain, and loss of the eye. Central retinal vein occlusion can produce macular edema and neovascularization in the back of the eye leading to vitreous hemorrhage and retinal detachment.
The Rho family GTPases regulates axon growth and regeneration. Inactivation of Rho with Clostridium botulinum C3 exotransferase (hereinafter simply referred to as C3) can stimulate regeneration and sprouting of injured axons; C3 is a toxin purified from Clostridium botulinum (see Saito et al., 1995, FEBS Lett 371:105-109; Wilde et al 2000. J. Biol. Chem. 275:16478). Compounds of the C3 family from Clostridium botulinum inactivate Rho by ADP-ribosylation and thus act as antagonists of Rho effect or function (Rho antagonists).
Degeneration of components of the retina can lead to partial or total blindness. Macular degeneration is a degeneration of the macular region of the retina in the eye. Degeneration of the macula causes a decrease in acute vision and can lead to eventual loss of acute vision. The wet form of macular degeneration is related to abnormal growth of blood vessels in the retina that can leak blood and can cause damage to photoreceptor cells.
Age-related macular degeneration (AMD) is a collection of clinically recognizable ocular findings that can lead to blindness.
Macular degeneration is a group of diseases that affect the central retina, or macula. There are two basic types of macular degeneration: “wet” and “dry”. In wet macular degeneration, there is an abnormal growth of new blood vessels. These new blood vessels break and leak fluid, causing damage to the central retina. This form of macular degeneration is often associated with aging. Approximately 90% of macular degeneration cases are dry macular degeneration. Vision loss can result from the accumulation of deposits in the retina called drusen, and from the death of photoreceptor cells. This process can lead to thinning and drying of the retina.
The findings of AMD include the presence of drusen, retinal pigment epithelial disturbance, including pigment clumping and/or dropout, retinal pigment epithelial detachment, geographic atrophy, subretinal neovascularization and disciform scar. Age-related macular degeneration is a leading cause of presently incurable blindness, particularly in persons over 55 years of age. Approximately one in four persons age 65 or over have signs of age-related maculopathy, and about 7% of persons age 75 or over have advanced macular degeneration with vision loss.
Drusen are opthalmoscopically visible, yellow-white hyaline excrescences or nodules of Bruch's membrane. Bruch's membrane lies beneath the retina and the adjacent retina pigment epithelium layer. Fat accumulates in Bruch's membrane with age and may contribute to the formation of drusen.
Drusen can occur in two forms. One form comprises hard, small (less than about 60 micrometers in diameter) drusen which do not increase with age and which do not predispose to macular degeneration. Another form comprises soft, large (more than about 63 micrometers in diameter) drusen which enlarge and become confluent with age. The soft, large drusen may predispose to macular degeneration, and are commonly seen in eyes of people with advanced macular degeneration in at least their other eye.
Drusen may be metabolic waste products from various layers of the retina such as from the retina, retina pigment epithelium, and choriocapillaris. Drusen may be yellow, white, gray, refractile, and/or pink. Drusen may be small, medium or large in size. Drusen may be regular or irregular, or symmetrical or asymmetrical in shape. A patient who has drusen and who suffers complications in one eye may suffer no complications in the other eye. Complications may comprise one or more conditions selected from the group consisting of retina pigment epithelium atrophy, choroid neovascularization, retina detachment serous, and retina detachment hemorrhagic. Drusen may affect contrast sensitivity, and may reduce the eye's ability to see adequately to allow a person to read in dim light or to see sufficient detail to permit a person to drive an automobile safely at night.
Not all these manifestations are needed for AMD to be considered present, and drusen alone are not directly associated with vision loss. The amount of opthalmoscopically or photographically identifiable drusen increases with age. Most definitions of AMD include drusen as a requisite because of the association of drusen with vision-threatening lesions of AMD such as geographic atrophy, retinal pigment epithelial detachment and subretinal neovascularization.
While the exact causes of macular degeneration are not known, contributing factors have been identified. The collective result of the contributing factors is a disturbance between the photoreceptor cells and the tissues under the retina which nourish the photoreceptor cells, including the retinal pigment epithelium, which directly underlies and supports the photoreceptor cells, and the choroid, which underlies and nourishes the retinal pigment epithelium.
The retina and macula may be subjected to oxidative damage by oxidants such as free-radicals and singlet oxygen, 1O2. The macula contains polyunsaturated fatty acids and is exposed to light, including in the visible and near ultraviolet light spectrum high-energy blue light, which can photosensitize the conversion of triplet oxygen to singlet oxygen, an oxidizing agent capable of damaging the polyunsaturated fatty acids, DNA, proteins, lipids, and carbohydrates in the macula. Reaction products resulting from oxidative interactions between components of the retina and oxidizing agents may accumulate in the retinal pigment epithelium and contribute to macular degeneration. Certain antioxidant nutrients may reduce the risk of developing macular degeneration by reducing the formation of radicals and reactive oxygen by decomposition of hydrogen peroxide without generating radicals, by quenching active singlet oxygen, and by trapping and quenching radicals before they reach a cellular target.
Another factor which may be involved in the pathology of macular degeneration comprises an elevated serum concentration of low density cholesterol lipoprotein (LDL). Low density lipoprotein cholesterol can be oxidized by an oxidizing agent to form oxidized LDL, which is found in atherosclerotic plaques. These oxidized products may accumulate as deposits in healthy retinal pigment epithelium and cause necrosis or death of functioning tissue. LDL cholesterol may also form atherosclerotic plaques in the blood vessels of the retinal and subretinal tissue, inducing hypoxia in the tissue, resulting in neovascularization. Postmenopausal women given unopposed estrogen replacement therapy can have a reduced risk of neovascular age-related macular degeneration. Estrogen can increase the amount of high density lipoprotein cholesterol (HDL) in the blood, which may produce changes in the transport and metabolism of lipid-soluble antioxidants, and limit the accumulation of oxidized LDL cholesterol in the retinal and subretinal tissues and blood vessels.
A contributing and indicating factor of advanced macular degeneration is neovascularization of the choroid tissue underlying the photoreceptor cells in the macula. Healthy mature ocular vasculature is normally quiescent and exists in a state of homeostasis in which a balance is maintained between positive and negative mediators of angiogenisis in development of new vasculature. Macular degeneration, particularly in its advanced stages, is characterized by the pathological growth of new blood vessels in the choroid underlying the macula. Angiogenic blood vessels in the subretinal choroid can leak vision obscuring fluids, leading to blindness.
Angiogenisis in the choroid can be induced by the presence of cytokine growth factors such as basic fibroblast growth factor (bFGF). Hypoxia of retinal cells may induce the expression of such growth factors, wherein the hypoxia may be induced by cellular debris or drusen accumulated in the retinal pigment epithelium, by oxidative damage of retinal and subretinal tissue, or by deposits of oxidized LDL cholesterol.
Existing retinal and subretinal vascular endothelial cells can be activated by interaction of the cytokine growth factors, such as bFGF, with tyrosine kinase mediated receptors of the endothelial cells. The activated endothelial cells can increase in cellular proliferation and express several molecular agents, such as the integrin αvβ3, adhesion molecules, and proteolytic enzymes, which enable newly developed endothelial cells to extend through the surrounding tissue. The newly extended endothelial cells can form into vascular cords and eventually differentiate into mature blood vessels.
Currently, no treatment has been shown to be of benefit to the majority of people who have AMD. There is no therapy that can significantly slow the degenerative progression of macular degeneration, or which can inhibit or substantially reduce the rate of subretinal neovascularization and proliferation of neovascular tissue in the choroids under the macula of the eye. Most experimental forms of treatment address the wet form of AMD, and target specifically neovascularization. Laser photocoagulation of the subretinal neovascular membranes that occur in 10-15% of affected patients can benefit individuals with macular degeneration who develop acute, extrafoveal choroidal neovascularization. For dry AMD, high daily doses of antioxidants such vitamin C (500 mg), vitamin E (400 IU), beta carotene (15 mg), as well as zinc oxide (80 mg; high concentrations of zinc occur in ocular tissues, particularly the retina, pigment epithelium and choroid) may modestly reduce risk of progression of those who have intermediate-sized drusen, large drusen, or non-central geographic atrophy, or advanced macular degeneration in one eye.
A number of techniques have been disclosed for administration of drugs to the eye including the posterior region of the eye. For example, U.S. Pat. No. 5,707,643 relates to a biodegradable scleral plug that is inserted through an incision in the sclera into the vitreous body. For administration of a drug to the eye, the plug releases a drug into the vitreous body for treating the retina by diffusion through the vitreous body.
Another technique for administration of a drug to the eye is disclosed in U.S. Pat. No. 5,443,505 which discloses implants which can be placed in the suprachoroidal space over an avascular region of the eye such as the pars plana or a surgically induced avascular region. Another embodiment involves forming a partial thickness scleral flap over an avascular region, inserting an implant onto the remaining scleral bed, optionally with holes therein, and suturing closed the flap. The drug can diffuse into the vitreous region and the intraocular structure.
Another delivery approach for administration of a drug to the eye is direct injection. For the posterior segment of the eye, an intravitreal injection has been used to deliver drugs into the vitreous body. In this regard, U.S. Pat. No. 5,632,984 relates to a treatment of macular degeneration with various drugs by intraocular injection. For administration of a drug to the eye, drugs are preferably injected as microcapsules. Intraocular injection into the posterior segment of the eye can allow diffusion of the drug throughout the vitreous, the entire retina, the choroid and the opposing sclera. Additionally, U.S. Pat. No. 5,770,589 relates to treating macular degeneration by intravitreally injecting an anti-inflammatory into the vitreous humor for administration of a drug to the eye. Injections can be administered through the pars plana in order to minimize the damage to the eye while drug is delivered to the posterior segment.
Another delivery approach is by surgical procedure. For example, U.S. Pat. No. 5,767,079 relates to the treatment of ophthalmic disorders including macular holes and macular degeneration, by administration of TGF-β for example by placing an effective amount of the growth factor on the ophthalmic abnormality. In treating the macula and retina, for administration of a drug to the eye a surgical procedure involving a core vitrectomy or a complete pars plana vitrectomy is performed before the growth factor can be directly applied, presumably by administration to the sclera on the anterior segment of the eye at an avascular region or by administration to the sclera behind the retina via a surgical procedure through the vitreous body, retina, and choroids, a dramatic, highly invasive, technique usually suitable only where partial vision loss has already occurred or was imminently threatened.
Another delivery approach for administration of a drug to the eye is by use of a device and a cannula. For example, U.S. Pat. No. 5,273,530 relates to the intraretinal delivery and withdrawal of samples and a device therefor. Unlike direct intraocular injection techniques, the method disclosed in this patent avoids the use of a pars plana incision and instead uses an insertion path around the exterior of the orbit. The device, having a curved handle and a tip with collar, allows a cannula to be inserted through the posterior sclera and down into the subretinal space without passing through the vitreous body. The collar is stated to regulate the penetration to the desired depth. The device is taught to be adjustable to any part of the eye including the scleral area, the choroidal area, the subretinal area, the retinal area and the vitreous area.
Another delivery approach for administration of a drug to the eye is by intrascleral injection. For example, U.S. Pat. No. 6,397,849, the contents of which is hereby incorporated by reference in its entirety, discloses a method of intrascleral injection which comprises injecting into the scleral layer of an eye through a location on the exterior surface of the sclera which overlies retinal tissue an effective amount of a therapeutic or diagnostic material. Depending on the injection conditions, the material can form a depot within the scleral layer and diffuse into the underlying tissue layers such as the choroid and/or retina, and/or the material can be propelled through the scleral layer and into the underlying layers. Because the sclera moves with the entire eye including the retina, the site of deposit on the sclera remains constant relative to a point on the underlying retina, even as the eye moves within the eye socket to permit site specific delivery by depositing material into the sclera at a site overlying the macula, thereby allowing material to be delivered to the macula and surrounding tissues. The injection procedure employs a cannula or needle as well as needle-less particle/solution techniques. In a preferred embodiment, a cannula is inserted into the sclera in a rotational direction relative to the eye and not orthogonal to the surface of the sclera.
Another delivery approach for administration of a drug to the eye is disclosed in U.S. Pat. No. 6,299,895 which discloses a method for delivering a biologically active molecule to the eye comprising implanting a capsule periocularly in the sub-Tenon's space, the capsule comprising a core containing a cellular source of the biologically active molecule and a surrounding biocompatible jacket, the jacket permitting diffusion of the biologically active molecule into the eye, wherein the dosage of the biologically active molecule delivered is between 50 pg and 1000 ng per eye per patient per day. The biologically active molecule can be an anti-angiogenic factor, and a second biologically active molecule or peptide can be co-delivered from the capsule to the eye. The method is disclosed to be useful treating ophthalmic disorders including macular degeneration.
Other delivery approaches for administration of a drug to the eye which can be useful with compositions of the current invention are well known in the art. For example, U.S. Pat. No. 5,399,163 discloses a method of providing a jet injection by pressurizing a fluid injectant; U.S. Pat. No. 5,383,851 discloses a needleless injection device; U.S. Pat. No. 5,312,335 discloses a needleless injection system; U.S. Pat. No. 5,064,413 discloses an injection device; U.S. Pat. No. 4,941,880 discloses an ampule for non-invasive injecting of a medication; U.S. Pat. No. 4,790,824 discloses a non-invasive hypodermic injection device; U.S. Pat. No. 4,596,556 discloses a pressure-operated hypodermic injection apparatus; U.S. Pat. No. 4,487,603 discloses an implantable micro-infusion pump for dispensing medication at a controlled rate; U.S. Pat. No. 4,486,194 discloses a therapeutic device for administering medicants through the skin; U.S. Pat. No. 4,447,233 discloses a medication infusion pump for delivering medication at a precise infusion rate; U.S. Pat. No. 4,447,224 discloses a variable flow implantable infusion apparatus for continuous drug delivery; U.S. Pat. No. 4,439,196 discloses an osmotic drug delivery system having multi-chamber compartments; and U.S. Pat. No. 4,475,196 discloses an osmotic drug delivery system.